My World GIS
My World GIS
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Introduction to My World

This tour will teach you basic My World skills and guide you through a sample investigation. You can read it straight through, or print a copy and follow along in My World.

The tour has the following sections:

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A. Adding Layers to the Map

On the left side of the My World Window, you will see a list of data files, called the Data Library. The "World" library is shown by default, but you can choose different libraries using the Library menu. Once you choose a library, its contents are listed in the white space below. In the "World" Library, click and drag the folder marked "Countries" from the list of data files into the box to the right of it, as shown in Figure 1 below. This area is called the Layer List.

Tip: In addition to choosing pre-defined data libraries, you can also use the Library to choose from several pre-made Projects.


Figure 1. Adding a layer to the map

A box marked "Countries" will appear where you dropped the item, and a map of the world will appear just to the right of that. You can use the buttons and menu in this box to control the appearance of the "Countries" layer. You can also double-click on this box to open a window which gives you even more options on how to display the layer. This box is called the Layer Control Panel.

Now add a second layer by dragging the folder marked "World Cities" into the Layer List. If you drop the "World Cities" file above the "Countries" box in the list, the "World Cities" layer will appear on top of the "Countries" layer, and the cities will be drawn over the countries. If you drop it below the "Countries" box, the "World Cities" layer will be underneath the "Countries" layer, and the continent outlines will draw on top of the cities. For now, add "World Cities" above the "Countries" layer. See Figure 2 below for an illustration of this.


Figure 2. Adding a layer on top of or below another layer

Now you know how to add a Layer to the map, either in front of or behind an existing layer. Once layers have been added to the Layer List, you can always change which is on top of which by clicking and dragging their boxes (or the Layer Control Panel) up or down the Layer List.

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B. Moving Around on the Map

First, switch to Visualize mode by clicking on the "Visualize" mode button, as shown in Figure 3 below. Visualize is the mode used for looking at the Map and customizing its appearance.


Figure 3. Switching to Visualize mode

Next, select the Zoom In tool (the magnifying glass with the plus sign in it). Click on the map and drag to draw a rectangle around the Continental United States, as shown in Figure 4 below. Clicking and dragging a rectangle zooms the map to the selected area. You can also click once to zoom in and re-center the map on the point you clicked.


Figure 4. Zooming in on the Continental United States

To view the entire map again, click on the Zoom To All button, as shown in Figure 5 below. You can click on that button at any time to make all of the contents of your map visible.


Figure 5. Zooming back out to see the entire map

Now that you know how to get around, let's customize the Map's appearance.

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C. Customizing the Appearance of the Map

Let's begin by customizing the appearance of the "World Cities" layer by setting the field used to determine the color of each city in the layer. The Color menu contains all the available fields for the layer (these fields represent the columns of the dataset's data table-- more on that in a bit). Set the color attribute to "Population" using the Color menu as shown in Figure 6 below.

Figure 6. Setting the fill color attribute of the Countries Layer

Now you should see the map of the world with each city's color determined by its population: the darker the color, the higher the population. If you put the World Cities layer underneath of the Countries layer, it may be difficult to see. You can fix this by hiding the Countries layer: Click on the check box in the upper-left corner of the Countries Layer Control Panel, as shown in Figure 7 below.


Figure 7. Hiding the Countries layer to get a better view of the World Cities layer

When you hide the "Counties" layer, the country outlines dissapear from the map. You can make them visible again by re-checking the check box. Do this now.

On the map (shown in Figure7), notice that most of the cities on the map are white, because there aren't many cities with populations in between the low and high ends of the scale. We can fix this by changing how My World classifies the populations of the cities. Begin by selecting the World Cities layer by clicking on its name in its Layer Control Panel. You can tell when the Layer is selected because its Control Panel will appear with an orange border and a background color different from the other layers. Once you have selected the World Cities layer, click on the Edit Layer Appearance button, as shown in Figure8 below.

Figure 8. Editing the appearance of the "Countries" layer

This will open the Edit Layer Appearance window. This window contains lots of controls for customizing the appearance of Layers, but right now we're only interested in the Color tab. Be sure that the Color tab is selected.

Next, click on the Classify By menu and select Natural Breaks, then press the Apply button in the lower right hand corner of the window, as shown in Figure9 below. Natural Breaks divides the cities into categories so that the difference in population among cities in each category is minimized. It usually produces a better coloring of the map than other classification methods.

Figure 9. Changing the classification of the countries' population

Try changing some of the other settings in the Edit Layer Appearance window, and see what happens to the appearance of the map when you press the Apply button. You can see what the map looks like after changing the classification of population in Figure10 below.

Figure 10. The "Countries" layer colored by Population classified by Natural Breaks

Now that you know how to customize the Map's appearance, you're ready to continue on to examine the contents of the map layers.

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D. Examining the Contents of a Map Layer

Most datasets consist of a Data Table that contains all of its information. Looking at the data table is a good way to see what information is available for display (as we have seen, you can also see a list of the table's fields in the Color menu of the Layer Control Panel).

Begin by selecting the World Cities layer by clicking on its name in the Layer Control Panel. You can tell when the Layer is selected because its Control Panel will appear with an orange border and a background color different from the other layers. Once you have selected the World Cities layer, click on the Data Table button, as shown in Figure11 below.

Figure 11. Activating a Layer's Data Table


My World will display a data table that shows the contents of the World Cities dataset-- in this case, information about each city's name, country, population, and whether or not it is its country's capital. You can sort the information in this table by clicking on each column's title, as shown below in Figure12. Click once to sort in an ascending order, click a second time to sort in a descending order, and click a third time to cancel the sorting.

Figure 12. Sorting a Data Table

You can use the data table to create Selections of specific data that you want to highlight in the map. For example, to select the 10 most populous cities, sort the population column in descending order, and click-and-drag the mouse to highlight the top 10 cities in the list, as shown below in Figure13. Then click the "Make Selection From Rows" button, and give your new selection a name (e.g., "Most Populous Cities").

Figure 13. Making a Selection from Rows in a Data Table

After creating your selection, My World returns you to the map, where you will now notice your selection in the World Cities Layer Control Panel. If you look carefully at your map, you may see the most populous cities highlighted in yellow. To make these cities more visible, change the Highlight Mode to "Hide Unselected", as shown below in Figure14. This will display only the cities in that selection.

Figure 14. Hiding Unselected Values in the Map

Now you're ready to continue investigating the data.

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E. Investigating the Data

Let's explore the relationship between population and geography in the United States. To do this, we will need to add some additional layers. We will also learn to use Analyze Mode to create selections of U.S. Cities based on geographic features.

First, zoom in on the continental United States using the Zoom In tool to drag a box around the continental United States, as demonstrated earlier.

Next, return to Construct mode. In the Data Library, change the Library menu to the "United States" data library. Then, drag the "U.S. Cities" layer from the to the top of the Layer List, as shown in Figure15 below. (Be sure to add "U.S. Cities" above the "Countries" and "World Cities" layers; this will make it appear on top of those layers).

Figure 15. Adding the "U.S.Cities" layer to the top of the Layer List

Now that you have added "U.S. Cities" to the map, return to Visualize mode. Next, hide the "World Cities" layer by clicking on the check box in the upper-left corner of the Countries layer's Layer Control Panel, as demonstrated earlier.

Now, you are ready to analyze the "U.S. Cities" layer. Our first step will be to select all U.S. cities with populations of one million or greater. To do this, click on the tab for Analyze mode at the top of the My World Window, as shown below in Figure16.

Figure 16. Analyze Mode

In Analyze mode, you will see a list of analysis choices on the left. Go to the Select... folder and click on By Value, as shown below in Figure17. This feature allows you to query records in a given layer based on the value of a specific field. To select cities with populations over one million, follow the guided text and use the pulldown menus to construct your desired selection. For example:

Figure 17. Selecting data by value

You can name the result, or click "OK" and My World will suggest a name for you.

After performing the calculation, My World will return you to the map, having highlighted your selected cities in yellow. It may be hard to notice with all the other cities visible, so you can Hide Unselected cities using the pulldown menu in the U.S. Cities Layer Control Panel, as demonstrated earlier.

To identify the cities, choose the Get Information Tool from the toolbar. When you click it, My World will ask you which layer you want to identify; e.g., "U.S. Cities". Once you have done this, click on any city. This will give you a table containing all available data for each city. The information changes as you click on different cities. When you are finished, you can close the table.


What do you notice about the locations of these large cities? All but three are near coastlines. Are any close to rivers or lakes? To find out, return to Construct mode and add the "U.S. Rivers" and "U.S. Lakes" datasets to the Layer List (you should add them below the U.S. Cities layer so they don't cover the cities). Next, return to Visualize mode to continue investigating.

To see the lakes, choose a Fill Color by "Name". Now, notice that two interior cities (Chicago and Detroit) are near rivers and lakes. Notice that all but one of these large cities are near some sort of major waterway. Can you find the one large city that is near neither a coast, nor river, nor lake?

Next, try creating selections for cities with populations of 500,000 or larger. Try the same for cities with populations of 250,000. As you do this, My World adds selections to the Layer Control Panel. You can click back and forth to see the different selections, as shown below in Figure18.


Figure 18. Changing selections within a layer

As you explore cities of different sizes, does the pattern hold? Are there exceptions?

You can continue exploring this data on your own. For example, try adding U.S. Highways to your map and seeing how this data relates to urban populations.


To learn how to save your work see the the My World tutorial on "How to Save your Work." You can find this and other useful tutorials by clicking on the Windows menu and selecting the Welcome Window, as show in Figure19 below.

Figure 19. Reopening the Welcome Window

The Welcome Window, shown in Figure20 below, contains links to a variety of useful resources to help you use My World.

Figure 20. Using the Welcome Window to access My World resources

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Last Updated: 2007-03-04 04:19:17

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